What are the tools and libraries that work for Gitlab ?
If you want to see packages to interfere with Git, see its own git page.
Get the list of opened issues, insert at "Fixes #"
See git-commit-insert-issue, which works for Github and Gitlab. It has a commit minor mode and an interactive function to fetche the opened issues of the current project when you type something like "Fixes #" in the commit message.